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Regular vs. Premium: Understanding Fuel

Understanding the differences between regular and premium grades of fuel is the best way to save yourself a good chunk of your hard-earned cash – either at the pumps, or at the garage later on down the road.

Different engines require different types of fuel, and when gasoline prices soar, it may be tempting to switch down to the lower grade regular fuel, even when your vehicle may call for a mid-level or premium grade fuel. But is this worth it to your potential maintenance costs down the road?

New engine technology means that your vehicle won’t audibly choke and putter if you change your fuel type regularly according to pump price, but do they hum and haw internally? Yes, and no.

In short, the difference between the two fuel grades is the blend of hydrocarbons used to make the fuel, and which combinations of additives are added to the mix. Let’s investigate further:

Octane

The perception of the fuel grade choice is often reduced to people interpreting the ‘premium’ grade as a superior fuel, packing more oomph and having the potential to increase fuel economy. That’s not necessarily true: premium fuel contains no more energy than regular gasoline.

The octane rating on the pumps represents the standard measure of performance capabilities of an engine – not the fuel itself. In general, the higher the octane number, the more compression the fuel can tolerate before bursting into ignition within the engine. As a result, higher performance engines, such as the 2016 Camaro, that hold higher compression ratios benefit from the increased octane because it complements the makeup of the engine.

Further, premium fuel and the more aggressive engines that call for the increased octane work together to extract as much power from each liter of gasoline as possible. Feeding such an engine the regular gasoline alternative means the motor will ‘knock,’ meaning the fuel in the cylinder head is unable to burn evenly, and instead detonates before it can be sparked by the sparkplugs.

The majority of new cars are equipped with knock sensors that allow the motor to tailor the engine controller to identify a knock in each individual cylinder – helping to provide peak efficiency from any grade of gasoline while fighting to stop potential damage that engine knocking can cause.

So in short, some cars benefit from higher octane premium fuels, while other do not.

Additives

Gasoline is made up of hydrocarbons produced in a catalytic reformer. The refinery process breaks down the crude oil’s large hydrocarbon molecules further by vaporizing them. Additives are included in the fuel blend for many reasons, namely, to reduce engine carbon build-up, improve combustion, inhibit corrosion and to allow for easier ignition in adverse weather conditions.

Ethanol is one such additive that boosts a fuel’s octane number. While it is generally added in high performance, high octane fuels, it translates to less energy per liter than gasoline, it possesses a much higher octane number – around 108 to premium fuel’s 97.

Other additives include detergents, metal deactivators, antioxidants and oxygenates. All petrol fuels contain additives, but some are more directly related to increasing combustion ratios for high octane thirsty motors.

Effects

To sum up the difference in fuel types from a user-friendly standpoint, your vehicle’s user manual may state that the ‘recommended’ fuel type is premium, rather than telling you it is required. Over time your engine will adjust to running on a lower octane fuel type, inevitably reducing the performance of the car, as well as its fuel economy. In this regard, it’s likely that the poorer fuel economy figures will be outweighed by the saving’s at the pump.

Ideally, you shouldn’t run a vehicle on a higher octane fuel that is called for, and vice versa, because engines are optimized to run efficiently on a specific grade of fuel. Always follow the recommended fuel type prompts in your vehicle’s user manual, and inside the gas cap. Doing so will reduce the likelihood that you’ll cause damage to a higher compression performance tuned engine. Oppositely, refraining from filling your modest hatchback with high octane fuel will ensure that you save your money at the pumps.

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